Embolic coil implant system and implantation method

ABSTRACT

Embolic coil implant systems and methods whereby coils are mechanically detachable are disclosed. The coils include a retention element that may be releasably retained within the distal end of an implant tool. The implant tool may include a fulcrum configured to engage a first filament and prevent the release of the coil when the first filament is engaged. Alternatively, an urging means and aperture may be disposed within the sidewall of the implant tool, and a first filament may, in conjunction with the aperture and sidewall, releasably retain the coil until the first filament is withdrawn. The implant tool may also include an alignment member for aligning the first filament.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/498,752 (Attorney Docket No. 41507-707.201), filed Jul. 7, 2009,which claims priority to Provisional Application No. 61/080,742,(Attorney Docket No. 41507-707.101), filed Jul. 15, 2008, andProvisional Application No. 61/083,111 (Attorney Docket No.41507-708.101), filed Jul. 23, 2008, the disclosures of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates generally to the fields of systems andmethods for implanting an intravascular implant device, and morespecifically to systems and methods for implanting embolic coils.

BRIEF SUMMARY OF THE INVENTION

Coil embolization is a commonly practiced technique for treatment ofbrain aneurysm, arterio-venous malformation, and other conditions forwhich vessel occlusion is a desired treatment option, such as, forexample, in the occlusion of a tumor “feeder” vessel. A typicalocclusion coil is a wire coil having an elongate primary shape withwindings coiled around a longitudinal axis. In the aneurysm coilembolization procedure, a catheter is introduced into the femoral arteryand navigated through the vascular system under fluoroscopicvisualization. The coil in the primary shape is positioned within thecatheter. The catheter distal end is positioned at the site of ananeurysm within the brain. The coil is passed from the catheter into theaneurysm. Once released from the catheter, the coil assumes a secondaryshape selected to optimize filling of the aneurysm cavity. Multiplecoils may be introduced into a single aneurysm cavity for optimalfilling of the cavity. The deployed coils serve to block blood flow intothe aneurysm and reinforce the aneurysm against rupture.

One form of delivery system used to deliver an embolic coil through acatheter to an implant site includes a wire and a coil attached to thewire. The coil (with the attached wire) is advanced through a catheteras discussed above. To release the coil into an aneurysm, current ispassed through the wire, causing electrolytic detachment of the coilfrom the wire. A similar system is used to deliver a coil to the site ofan arterio-venous malformation or fistula. The subject system provides amechanical alternative to prior art electrolytic detachment systems.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of an embolic coil implant system;

FIG. 2 is a side elevation view of the embolic coil of the implantsystem of FIG. 1;

FIG. 3A-3C are a series of side elevation views of the portion of thecoil identified by region 3-3 in FIG. 2, illustrating the properties ofthe pre-tensioned stretch resistant wire.

FIG. 4A illustrates the proximal portion of the coil engaged with thedistal portion of the detachment shaft and wire.

FIG. 4B is similar to FIG. 4A and illustrates the proximal portion ofthe coil and the distal portion of the shaft and wire followingdetachment.

FIGS. 5A through 5G are a sequence of drawings schematicallyillustrating the steps of occluding an aneurysm using the system ofFIGS. 1 through 4B.

FIGS. 6A and 6B schematically illustrate steps of detaching the coilfrom the detachment shall and wire in accordance with the method ofFIGS. 5A through 5G.

FIG. 7 is an elevation view of an alternate embodiment of a detachmentsystem, in which the distal end of the pusher tube is shown partiallytransparent.

FIG. 8 is a perspective view of the embodiment of FIG. 7.

FIG. 9 is a plan view of the system of FIG. 7, showing the coil detachedfrom the pusher tube.

FIG. 10 is an elevation view of the system of FIG. 7, showing the coildetached from the pusher tube.

FIG. 11 is a side elevation view of yet another embodiment of adetachment system according to the invention, in which the distal end ofthe pusher tube is shown partially transparent.

FIG. 12 is a plan view of the embodiment of FIG. 11.

FIG. 13 is a bottom view of the embodiment of FIG. 11.

FIG. 14 is a side elevation view of the embodiment of FIG. 11 followinga step in detachment of the embolic coil.

FIG. 15 is a side elevation view of the embodiment of FIG. 11 followingdetachment of an embolic coil.

FIG. 16 is a side elevation view of yet another alternative embodimentaccording to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, general components of an embolic coil implantsystem 10 include a microcatheter 12, insertion tool 14, and emboliccoil 16. These components may be provided individually or packagedtogether. Additional components of the system may include a guidecatheter insertable into the vasculature via an access point (e.g.,femoral puncture), and an associated guide wire for facilitatingadvancement of the guide catheter.

Microcatheter 12 is an elongate flexible catheter proportioned to bereceived within the lumen of a corresponding guide catheter and advancedbeyond the distal end of the guide catheter to the cerebral vasculaturewhere an aneurysm to be treated is located. Suitable dimensions for themicrocatheter include inner diameters of 0.010″ to 0.045″, outerdiameters of 0.024″ to 0.056″, and lengths from 75 cm to 175 cm. Onepreferred embodiment utilizes the following dimensions: 0.025 in ID,0.039 in Distal OD (3 F), 0.045 in Proximal OD (3.5 F), and length of145-155 cm. Marker bands 18 facilitate fluoroscopic visualization of themicrocatheter position during the course of an implantation procedure.Microcatheter 12 includes a lumen 20 proportioned to receive the emboliccoil 16 and the shaft of the insertion tool 14. When the coil is withinthe lumen of the microcatheter, the surrounding lumen walls restrain thecoil in the generally elongated shape shown in FIG. 1. Release of thecoil from the microcatheter allows the coil to assume its secondaryshape.

Details of the embolic coil 16 are shown in FIG. 2. Coil 16 is formed ofa wire 22 coiled to have a primary coil diameter D1 of approximately0.020 inches, although smaller diameters, and diameters as large as0.035 inches, may instead be used. The pitch of the coil may be uniformas shown, or it may vary along the length of the coil, or differentsections of the coil may be formed to have different pitches. The wirematerial selected for the coil is preferably one capable of fluoroscopicvisualization, such as Platinum/Iridium, Platinum/Tungsten, or othersuitable material. In one embodiment, the wire forming the coil has adiameter of approximately 0.0015-0.0020 inches. Coil 16 is then formedinto a secondary three-dimensional shape. The secondary shape can behelical, spherical, multi-lobal or any other shape desired to fill theaneurysm void. The process for forming this shape is to temperature setthe stretch resistant wire 30 into the desired shape. Thestretch-resistant member could be a shape-memory polymer or metal suchas nitinol. Stretch-resistant member 30 can be in a diameter range of0.0005″ to 0.003″.

One or more reduced-diameter windings 24 are positioned at the proximalend of the coil 16, forming a stop 26. An atraumatic distal tip 28,which may be formed of gold or tin solder or other material, is mountedto the distal end of the coil 16. A stretch resistant wire 30 or othertype of elongate filament or strand is attached to the distal tip 28 andextends through the coil 16. Stretch resistant wire 30 includes anelement 32 on its proximal end that is sufficiently broad that it willnot pass through the lumen of the windings of stop 26, but will insteadrest against the stop 26. Element 32 may be a ball (e.g., formed ofgold/tin solder, PET, platinum, titanium or stainless steel) as shown,or an alternative element having features that will engage with or beunable to pass the stop 26 or other parts of the proximal portion of thecoil 16. The stretch resistant wire helps to maintain the pitch of thecoil even when the coil is placed under tension. During implantation,the stretch resistant wire helps in repositioning of the coil (ifneeded). The stretch resistant wire makes the coil easier to retract,and maintains close positioning of coil windings during manipulation ofthe coil.

Stretch resistant wire 30 is pre-tensioned, so that the ball 32naturally sits firmly against the stop 26 as shown in FIG. 3A. Whentension is applied to the wire 30 as shown in FIG. 3B, and then releasedas in FIG. 3C, the ball will return to its firm seating against thestop. The stretch resistant wire prevents the coil from stretching whendeployed, repositioned, or withdrawn from the aneurysm. This stretchresistant wire will not yield when placed in tension duringrepositioning. Conversely, stretch resistant wire will preventcompaction of adjacent coils, likely improving long term performance ofcoil 16 following implantation. Stretch resistant wire 30 will have ayield strength approximately 0.5 lbs. In a preferred embodiment, thestretch resistant wire is shape set to give the embolic coil 16 itspredetermined secondary shape. In other words, the shape set of the wirewill cause the coil 16 to assume the secondary shape (FIG. 5C) once itis advanced from the microcatheter 12. In alternative embodiments, thecoil itself, or both the coil and the wire may be shape set to give thecoil its secondary shape.

Referring again to FIG. 1, insertion tool 14 includes a flexibleelongate tubular shaft 34, and a handle 36 on the proximal portion ofthe shaft 34. An actuator 38 on the handle 36 is manipulatable by a userto effect detachment of an embolic coil from the shaft 34 as will bediscussed in detail below. Although the actuator is shown in thisdrawing as a slidable button, any number of other types of slidable,rotatable, pivotable, depressible, etc., actuators may instead be usedusing techniques well known in the art. Although the handle 36 is showncoupled to insertion tool 14, in other embodiments, the handle 36 may beattached and removed for use with multiple coils to effect detachment.

FIGS. 4A and 4B show cross-section views of the distal portion of theshaft 34. As shown, a detachment wire 40 or other type of elongatefilament or strand extends through the lumen of the shaft 34. Duringuse, shaft 34 would be inserted through microcatheter 12 to theaneurysm. A pair of engaging elements 42 is positioned on the wire 40.Engaging elements 42 are elements that will couple the detachment wire40 to the stretch resistant wire 30, preferably by engaging the element32. In the illustrated embodiment, the engaging elements 42 are spacedapart elements having a broader diameter than the wire. Suitableexamples include spaced apart beads 42 deposited onto the wire. Thesemay be formed of gold/tin solder, PET, stainless steel, or alternatematerials.

As shown in FIG. 4A, embolic coil 16 is coupled to the insertion tool 14by positioning ball 32 between the engaging elements 42 within the shaft34. The ball 32 is constrained between the engagement elements 42 andthe surrounding walls of the shaft lumen. This positioning retracts theball 32 proximally relative to the coil 16, adding tension to thestretch resistant wire 30.

Referring to FIG. 4B, to release the embolic coil 16 from the insertiontool 14, the actuator is manipulated to cause relative advancement ofthe detachment wire 40 relative to the shaft 34. In other words, theactuator may withdraw the shaft and/or advance the wire 40. Otherembodiments may be provided without an actuator, in which case the usermay manually advance the wire 40 and/or retract the shaft 34. The moreproximal sections of the wire 40 and/or shaft 34 may be thicker than thedistal sections as shown in FIGS. 6A and 6B to facilitate manualactuation by the user's fingers or by an actuator.

The relative movement between the shaft and wire causes the distalportion of the wire 40 to extend from the shaft, thereby releasing theconstraints on the ball 32. The ball 32 and attached stretch resistantwire 30 retract towards the coil 16, and the ball 32 comes to rest atthe stop 26.

FIGS. 5A through 5G illustrate use of the system to implant the coil 16.Prior to implantation, the coil is coupled to the insertion tool 14 asillustrated in FIG. 1.

The microcatheter 12 is introduced into the vasculature using apercutaneous access point, and it is advanced to the cerebralvasculature. As discussed above, a guide catheter and/or guide wire maybe used to facilitate advancement of the microcatheter. Themicrocatheter is advanced until its distal end is positioned at theaneurysm A. FIG. 5A.

The coil 16 is advanced through the microcatheter 12 to the aneurysm A.FIG. 5B. The coil and insertion tool may be pre-positioned within themicrocatheter 12 prior to introduction of the microcatheter 12 into thevasculature, or they may be passed into the proximal opening of themicrocatheter lumen after the microcatheter has been positioned withinthe body. The insertion tool 14 is advanced within the microcatheter 12to deploy the coil from the microcatheter into the aneurysm A. As thecoil exits the microcatheter, it assumes its secondary shape as shown inFIG. 5C due to the shape set of the stretch resistant wire 30.

Referring to FIG. 6A, the detachment wire 40 may includefluoroscopically visible markers that indicate to the user when the coilhas been advanced sufficiently for detachment. For example, the user maywatch for alignment of a marker 44 on the wire 40 with the markers 18 onthe microcatheter. Note, however, that the detachment step may beperformed with the proximal end of the coil inside or outside themicrocatheter.

At the appropriate time, the coil is released from the insertion tool bywithdrawing the shaft 34 relative to the detachment wire 30 to cause thedistal end of the wire to extend from the shaft 34. FIGS. 5D and 6Billustrate retraction of the shaft 34 while holding the wire 30stationary, although the detachment may instead be performed byadvancing the wire while holding the shaft stationary, or by combinedmotion of retracting the shaft and advancing the wire. The coil detachesfrom the wire 30, and the ball 32 of the coil 16 retracts into contactwith the stop 26. FIG. 5E. The insertion tool 14 is withdrawn from themicrocatheter 12. FIG. 5F. If additional coils are to be implanted, aninsertion tool 14 with an attached coil is passed into the microcatheter12 and the steps of FIGS. 5B through 5E are repeated. The method isrepeated for each additional coil need to sufficiently fill the aneurysmA. Once the aneurysm is fully occluded, the microcatheter 12 is removed.FIG. 5G.

FIGS. 7-10 illustrate an alternative embodiment of an insertion tool 114that may be used to deploy the embolic coil 16 in the manner similar tothat shown in FIGS. 5A-5G.

Referring to FIG. 7, the insertion tool 114 comprises an elongate pushertube 116 having a tubular distal tip 118 (shown partially transparent inFIG. 7). A fulcrum 120 having a slot 122 (best shown in FIG. 9) is cutinto a side wall of the distal tip 118. The distal end of the fulcrumcan be moved into an inwardly-extending position in which it extendsinto the lumen of the distal tip 118 as shown in FIGS. 7 and 8. Thefulcrum 120 is shape set to return to an open (or neutral) positiongenerally flush with the pusher tube wall (FIG. 9) when it is releasedfrom the inwardly-extending position. A pull wire 126 is extendablethrough the lumen of the pusher tube 116 and into the slot 122 in thefulcrum 120 to retain the fulcrum in the inwardly-extending positionshown in FIGS. 7 and 8.

The distal tip 118 is preferably formed of shape memory material such asnitinol, shape memory polymer, or an injection molded material havingelastic properties. The more proximal sections of the pusher tube 116can be made of polymeric tubing, with the distal tip 118 mounted topolymeric tubing. In the illustrated embodiment, the distal tip 118includes a plurality of proximally-extending fingers 124 laminated intothe polymeric tubing of the pusher tube 116 to secure the distal tip inplace.

To couple the pusher tube 116 and coil 16 for use, the pull wire 126 isintroduced into the pusher tube. Ball 32 is separated slightly from thecoil 16 and is inserted into the pusher tube 116 and held in place whilethe fulcrum 120 is pressed into the inwardly-extending position toprevent movement of the ball 32 out of the distal tip 118. The pull wire126 is passed through the slot 122 to retain the fulcrum in theinwardly-extending position.

To deploy the coil 16, the coil and pusher tube 116 are passed through adelivery catheter as described above. At the site of the aneurysm, thepusher tube 116 is advanced to push the coil out of the deliverycatheter. The pull wire 126 is pulled proximally from the slot 122 ofthe fulcrum 120, allowing the fulcrum 120 to return to its open positionand out of contact with the ball 32. As with the previous embodiments,the ball 32 retracts into contact with the proximal end of the coil 16and in doing so exits the proximal end of the pusher tube 116.

FIGS. 11-15 illustrate another alternate embodiment of a detachmentsystem. FIGS. 11, 14 and 15 illustrate detachment system 200 followingsuccessive steps to detach embolic coil 206 from insertion tool 214.Beginning with FIG. 11, a side elevation view of the distal end ofinsertion tool 214 is shown as partially transparent. Insertion tool 214comprises an elongate pusher tube 216 having a tubular distal tip 218,and side wall 204 defining lumen 208 therethrough. Side wall 204 is cut,molded, or otherwise configured to define paddle 240, partial aperture244 surrounding a portion of paddle 240, and shoulder 246. Paddle 240and partial aperture 244 may be of various alternative sizes and/orshapes. An example of a suitable shape for paddle 240 can be seen in aplan view in FIG. 12, which also reveals a possible position of ball 232prior to deployment of system 200. As explained in greater detail below,prior to deployment of system 200 to release coil 206, ball 232 hasfreedom of movement within lumen 208, both axially and rotationally. Theexact position of ball 232 will consequently vary from that illustratedin FIG. 12.

Also cut or otherwise configured or disposed upon a side wall 204 isalignment member 228, shown in the example of FIG. 11 as opposite paddle240. As seen from a bottom view of the device in FIG. 13, alignmentmember is illustrated as a loop cut from sidewall 204. Alternatively, analignment member may be formed by placing one or more circumferentialcuts into the sidewall to define a band and bending the band inwardlyinto the lumen. It will be appreciated that alignment member 228 mayalternatively be, for example, a hook, tab, or any other suitablestructure for guiding the position of pull wire 226. Pull wire 226 isaxially moveable within alignment member 228, however, alignment member228 helps prevent unintended longitudinal translation of pull wire 226.

In preparation for deploying system 200, pull wire 226 is loaded throughalignment member 228, through lumen 208, until it reaches ball 232, oras far as coil 206. Prior to loading coil 206, pull wire 226, which maybe tapered, may be threaded through the distal end of insertion tool 214to permit loading of ball 232, and then retracted slightly to releasablyretain coil 206. When positioned within distal tip 218 via alignmentmember 228, and occupying lumen 208 pull wire 226 urges ball 232 againstpaddle 240, and ball has freedom of movement within aperture 244.Partial aperture 244 permits paddle 240 to be urged slightly out of theplane of sidewall 204, and paddle 240 in turn places some pressure onball 232. Ball 232 is prevented by shoulder 246 from exiting the distaltip 218. Though ball 232 is retained within distal tip of insertion tool214 prior to deployment of system 200, ball 232 advantageously has bothaxial and rotational freedom of movement within the distal tip 218 ofinsertion tool 214 prior to retraction of pull wire 226 by an operator.

As shown in FIG. 14, during deployment of detachment system 200, pullwire 226 is retracted proximally of ball 232. (Alternatively, insertiontool 214 may be moved distally to pull wire 226.) Once pull wire 226 isproximal of ball 232, ball 232 is urged by paddle 240 into the lumen 208of insertion tool 214. Axial movement of ball 232 is no longerrestricted in a distal direction by shoulder 246, and ball 232 (andhence coil 206) is free to exit distal tip 218. FIG. 15 illustrates coil206 following its exit from distal tip 218.

FIG. 16 illustrates a similar detachment mechanism which operatesgenerally according to the same principles of the embodiment describedin relation to FIGS. 11-15 above. However, in the embodiment illustratedin FIG. 16, paddle 340 is oriented perpendicularly to the longitudinalaccess of insertion tool 214. Further, no aperture surrounds paddle 340.Other, alternative configurations of paddle 340 are also possibleaccording to the invention.

What is claimed is:
 1. An embolic coil deployment system, comprising: animplant tool including a shaft having a lumen, a first filament disposedin the lumen, and at least one engaging element on the first filament;and an implant including a coil and a second filament extending throughthe coil, the second filament including a distal end coupled to the coiland a proximal end including a retention clement disposed in the lumenof the shaft, the retention element positioned in contact with andreleasably restrained in a restrained position by the engaging elementand a sidewall of the lumen.
 2. The system of claim 1, wherein theengaging element includes a pair of broadened elements on the firstfilament, and wherein the retention element of the implant is releasablyrestrained between the broadened elements and the sidewall of the lumen.3. The system of claim 1, further including a catheter, wherein theimplant tool and implant are positionable within the catheter.
 4. Thesystem of claim 1, wherein the second filament is a stretch-resistantwire.
 5. The system of claim 1, wherein the first filament and shaft arerelatively moveable between a first position in which the distal portionof the first filament is within the shaft and a second position in whicha distal portion of the first filament extends distally from the lumenby an amount sufficient to release the retention element from therestrained position.
 6. The system of claim 1, wherein the secondfilament is in tension such that release of the retention element fromthe restrained position causes the retention element to retract intocontact with a proximal portion of the implant.
 7. The system of claim6, wherein the implant includes a stop on a proximal portion of thecoil, and wherein release of the retention element from the restrainedposition cause the retention clement to retract into contact with thestop.
 8. An embolic coil deployment system comprising: an implant toolincluding a shaft having a lumen, a sidewall, at least one fulcrum, anda first filament disposed in the lumen; and an implant including a coiland a second filament extending through the coil, the second filamentincluding a distal end coupled to the coil and a proximal end includinga retention element disposed in the lumen of the shaft, the retentionelement positioned in contact with and releaseably retained within thelumen by the first filament and the fulcrum.
 9. The system of claim 1,wherein said fulcrum comprises at least one aperture for releaseablyreceiving said first filament.
 10. The system of claim 1, wherein saidfirst filament is moveable from a first position in which the firstfilament is engaged with said fulcrum, and a second position in whichsaid first filament is disengaged from said fulcrum.
 11. The system ofclaim 10, wherein in said first position said fulcrum releaseablyretains said retention element within the lumen, and when in said secondposition, said fulcrum does not retain said retention element within thelumen.
 12. The system of claim 1, wherein said fulcrum comprises a firstand second aperture for releaseably receiving said first filament, saidfirst filament is moveable from a first position in which said firstfilament depresses said fulcrum into the lumen distal to said retentionelement thereby releasably retaining the retention element within thelumen, and a second position whereby said first filament is retracted ina proximal direction to release said fulcrum, thereby releasing saidretention element from the lumen.
 13. The system of claim 1, whereinsaid fulcrum is formed with the side wall of the implant tool.
 14. Amethod of implanting an embolic coil, comprising the steps of: providingan implant tool including a shaft having a lumen, a first filamentdisposed in the lumen, and at least one engaging element on the firstfilament; providing an implant including a coil and a second filamentextending through the coil, the second filament including a distal endcoupled to the coil and a proximal end including a retention element;coupling the implant and implant tool by introducing the retentionelement into the lumen of the shaft, the retention element andpositioning the retention element in a restrained position between theengaging element and a sidewall of the lumen; advancing the implant andimplant tool intravascularly to an implant site; effecting relativelongitudinal movement between the shaft and the first filament such thata distal portion of the first filament extends proximally into the lumenby an amount sufficient to release the retention element from therestrained position; and removing the implant tool, leaving the implantat the implant site.
 15. The method of claim 14, wherein: providing theimplant includes providing the coil to include a proximal stop andproviding the retention element seated against the step; introducing theretention element implant tool includes pulling the first filament in aproximal direction to separate the retention element from the stop, andrestraining the first filament in tension within the lumen; andreleasing the retention element from the restrained position causes theretention element to retract into contact with the stop.
 16. The methodof claim 14, wherein the implant includes an elongate primary shape andan expanded secondary shape, and wherein the method includes:positioning the implant within a catheter, the implant in the catheterhaving the primary shape; and advancing the implant from the catheter atthe implant site, causing the implant to expand to the secondary shape.17. A method of implanting an embolic coil, comprising the steps of:providing an implant tool including a shaft having a lumen, a side wall,at least one engaging element and a first filament disposed in thelumen; providing an implant including a coil and a second filamentextending through the coil, the second filament including a distal endcoupled to the coil and a proximal end including a retention element;coupling the implant and implant tool by introducing the retentionelement into the lumen of the shaft, and positioning the retentionelement in a releaseably retained position between the fulcrum and asidewall of the lumen; advancing the implant and implant toolintravascularly to an implant site; effecting relative longitudinalmovement between the shaft and the first filament such that theretention element is not retained within the lumen; and removing theimplant tool, leaving the implant at the implant site.
 18. The method ofclaim 17, wherein the step of coupling the implant and implant toolcomprises releaseably engaging said first filament with said engagingelement.
 19. The method of claim 18, wherein said engaging elementcomprises a fulcrum.
 20. The method of claim 17, wherein said step ofcoupling the implant and implant tool comprises providing said firstfilament with at least one engaging element, and positioning saidengaging element to releaseably retain said retention element.